Formation and rearrangement of Sn(II) phosphanediide cages

The room-temperature reactions of Sn(NMe(2))(2) with less sterically demanding primary phosphines (RPH(2)) give the homoleptic phosphanediide compounds [SnPR](n) in high yields (R=tBu (1a), cyclohexyl (1b), 1-adamantyl (1c)). However, the room-temperature reaction of Mes*PH(2) (Mes*=2,4,6-tBu(3)C(6)H(2)) with Sn(NMe(2))(2) gives the model intermediate [{SnPMes*}(2)(mu-NMe(2))SnP(H)Mes*] (3), together with the product of complete deprotonation [SnPMes*](3) (4). Phosphorus--phosphorus bonded products are produced in these reactions at elevated temperatures. If the reaction producing 1a is heated to reflux then [tBuP(H)P(H)tBu] is produced as the major product (together with tin metal). The novel octanuclear cage [{SnPtBu}(7)Sn(PtBu)(3)] (2) can also be isolated in low yield, resulting from formal addition of the heterocyclic stannylene [(tBuP)(3)Sn] to a Sn-P single bond of the intact structure of 1a. Prolonged heating of the reaction producing 3 and 4 leads to the formation of the diphosphene [PMes*](2) (5) and tin metal. The X-ray structures of the heptamer 1a (n=7), octanuclear 2 and trinuclear 3 are reported.